This invention relates to a self-blocking hypodermic syringe for once-only use, which cannot be reused after it has been once used, and is provided with a needle protection cap which is automatically transferred into its protection position after use.
In medical practice, medicaments are frequently administered to the patient hypodermically by means of a needle and syringe.
In order to ensure maximum protection from infection and the like, sterile syringes for once-only use are usually employed, these being packaged in sealed containers to be opened at the moment of use.
However, syringes are also used by drug addicts for drug injection, and with this category of person a considerable increase has been noted in the spread of viral illnesses, such as type B hepatitis and acquired immunodeficiency syndrome (AIDS), the cause of which is the contagion transmitted by the use of the same syringe by more than one person, who ignore the rule which prescribes its once-only use.
Moreover when syringes are used to inject persons suffering from illnesses of the aforesaid type, it can sometimes happen that the medical functionary or whoever carries out the injection is accidentally injured by the used syringe needle either before fitting a protection cap onto the needle or while fitting it, or before placing the syringe in a closed container for its disposal, with the danger of contracting the infection.
Finally, syringes used by drug addicts for drug taking are very often carelessly thrown away in public places such as public gardens after use, so exposing park attendants and other persons, especially children, to the danger of accidental pricking and possible infection.
Certain syringes comprise means for controlling the plunger stroke within the cylindrical body for various reasons.
For example, GB-A-551 545 discloses a syringe comprising means for delaying or braking the plunger stroke within the cylindrical body and for enabling the user to determine the quantity of injected liquid by feel.
DE-A-3 107 414 discloses blocking means for preventing the extraction of a plunger from the cylindrical body in order to avoid contaminating the space which is to contain the liquid to be injected, and US-A-1 434 381 discloses a syringe provided with elastic braking or delay means to prevent accidental introduction of air into the liquid contained in the syringe or accidental leakage of this liquid, or again accidental escape of the plunger from the cylindrical body.
However, none of the known syringes comprises means for preventing the re-use of a once-only usable syringe or for preventing accidental pricking after the syringe has been used.
The problem therefore arises of preventing the spread of contagion by making it impossible to use the same syringe more than once, independently of the desire or negligence of the user, and of isolating the needle after the syringe has been used so that the needle is made safe.